66 Barracuda Formula S - Performance indicator instead of Tach?

Mine is a non- Formula S car with the commando engine and 4 speed with 8 3/4 rear end.

It came with a 150 mph speedo as part of the commando engine option but also came with a performance indicator.

From all things I have read, all S cars should have come with a tach.

Correct. My old 66 (lilcuda's car) was equipped like yours, but does have the tach.